Many Internet-based service providers deliver digital content to clients around the world. Digital content may include web objects (e.g., text, graphics, URLs, scripts), downloadable objects (e.g., media files, software, documents), web applications, streaming media (e.g. audio and video content), etc. Providing digital content to numerous clients that are located in a broad variety geographical locations can present challenges to service providers. For example, a service provider may be unable to provide sufficient server resources and/or network bandwidth to serve all clients requesting digital content at a given time. In addition, clients that are geographically remote from a service provider's servers may experience high levels of latency and/or low transfer rates as traffic between the service provider and the client is routed through a large number of Internet servers and over great geographical distances.
Content Delivery Networks (CDNs) aim to ease the ability of service providers to deliver digital content to large and/or geographically diverse groups of clients. CDNs position servers (or clusters of servers) in various geographical locations, and use these servers to cache and deliver content from origin servers of service providers. As such, CDNs can improve the service providers' ability to deliver content to clients both by increasing total available server resources and bandwidth used to deliver each service provider's content, and also by delivering each service provider's content from servers that are geographically nearer the clients that are being served.
CDNs often provide content delivery services for a large number of service providers. As such, CDNs allocate CDN resources among the various service providers. For example, if the CDN is experiencing a surge in traffic for a particular service provider in a particular geographical region, the CDN may reactively allocate additional server resources in the particular geographical region for use in delivering the particular service provider's content, while removing the additional server resources in the particular geographical region from one or more other service providers.